The invention relates to a clamping device for a band-shaped tensional member on a concrete surface of a supporting structure.
For increase in load capacity (strengthening) or for restoration to the original load capacity (reconstruction) of supporting structures made of reinforced concrete or prestressed concrete, it has been known to later attach prestressed tensional members on the outside of the supporting structure. For example, brackets made of steel or reinforced concrete are attached with dowels (bolts) to the concrete surface for anchoring and the tensional member is then tensioned between said brackets. However, through displacement between the axis of the tensional member and the concrete surface there develops an unfavorable displacement moment, which is to be taken up and transferred in the bracket anchoring; in addition, a bond between the tensional member and the concrete surface cannot be obtained.
The required prestress has to be applied to the band-shaped tensional member that rests on the concrete surface as long as the adhesive layer between the band-shaped tensional member and the concrete surface has not hardened (cured). Both ends of the prestressed band-shaped tensional member must be durably connected to the supporting structure. A clamping device of the present type serves for this purpose.
A clamping drive is necessary for the application of prestress, which has for instance one or more hydraulic cylinders. However, these clamping drives must be removable so that they can be reused again. Therefore durable anchoring of the band-shaped tensional member is necessary after completion of the clamping process. This anchoring should be made in such a manner that only a small part protrudes from the concrete surface to make protection against corrosion possible in a simple way.
It is therefore the object of the invention to provide a clamping device of the type mentioned in the beginning that makes possible in a simple manner the application of a prestress force and an effective anchoring of the band-shaped tensional member whereby the least possible number of components will remain permanently at the clamping site.
This object is achieved according to the invention whereby in a base mounting, which is durably joined to the supporting structure, there is a clamping slide detachably joined to the band-shaped tensional member by clamping and which, in turn, is arranged so it may be longitudinally guided and removed. A clamping drive is detachably mounted between the clamping slide and the base mounting, whereby at least one spacer may be inserted between facing abutment surfaces of the base mounting and the clamping slide, and whereby an anchoring device may be durably connected to the band-shaped tensional member and the base mounting.
The use of a clamping slide, which only temporarily engages the band-shaped tensional member during the clamping process, and an anchoring device which bonds permanently with the band-shaped tensional member only after the clamping process, make it possible to remove all components that are necessary for the clamping process after completion of the clamping process and to re-use said components for pre-stressing of additional band-shaped tensional members. The anchoring device, which remains continuously connected to the band-shaped member, may be designed having only a few simple components.
The base mounting preferably consists of a base plate and guides for the clamping slide that is detachably mounted thereon, preferably by bolts whereby said base plate may be advantageously and durably joined with the supporting structure by adhesion. This divided configuration of the base mounting makes possible to remove the guides after completion of the clamping process and to leave only the base plate permanently attached to the supporting structure whereby said guides are needed only temporarily during the clamping process.
According to a preferred embodiment of the invention, it is proposed that the clamping sled consist of a lower plate and a clamping plate bolted thereto whereby the band-shaped tensional member may be clamped in between. This configuration makes possible, on one hand, a simple clamping connection between the clamping slide and the band-shaped tensional member, and on the other hand, the clamping slide may be removed in a simple way from the band-shaped tensional member after completion of the clamping process and anchoring of said tensional member by an anchoring device.
According to another preferred embodiment of the invention, the anchoring device has a clamping anchor plate that may be bolted to the base plate while clamping down the band-shaped tensional member. Preferably, the clamping anchor plate may additionally be glued to the band-shaped tensional member.
This combination of clamping and gluing in the region of the anchoring device increases the safety of the tensile force transmission in the anchoring area since the adhesive bond is added to the static friction caused by the clamping pressure. Thereby a durable anchoring of the band-shaped tensional member is guaranteed even after decreasing the prestress forces of the bolt on the clamp. In addition, the problem of corrosion protection in the clamping joint is solved by the application of an adhesive.